Anhydrous, liquid phase process for preparing hydroxyl containing polymers of enhanced purity

ABSTRACT

An anhydrous, liquid phase process for preparing hydroxyl containing polymers of enhanced purity comprising the steps of polymerization, purification, transesterification, purification, catalyst removal, and solvent exchange. The resultant polymer in solution can be used directly, without further processing steps, to prepare a photoresist composition.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to processes for preparingsubstantially pure hydroxyl-containing polymers including homopolymers,and copolymers such as terpolymers and tetrapolymers in a liquid phaseoperation which is substantially anhydrous. These polymers are thenconverted into photoresist compositions for use as such.

[0003] 2. Description of the Prior Art

[0004] There is a desire in the industry for higher circuit density inmicroelectronic devices that are made using lithographic techniques. Onemethod of increasing the number of components per chip is to decreasethe minimum feature size on the chip, which requires higher lithographicresolutions. The use of shorter wavelength radiation (e.g., deep UV e.g.190 to 315 nm) than the currently employed mid-UV spectral range (e.g.350 nm to 450 nm) offers the potential for higher resolution. However,with deep UV radiation, fewer photons are transferred for the sameenergy dose and higher exposure doses are required to achieve the samedesired photochemical response. Further, current lithographic tools havegreatly attenuated output in the deep UV spectral region.

[0005] In order to improve sensitivity, several acid catalyzedchemically amplified resist compositions have been developed such asthose disclosed in U.S. Pat. No. 4,491,628 (Jan. 1, 1985) and Nalamasuet al, “An Overview of Resist Processing for Deep UV Lithography”, 3.Photopolymer Sci. Technol. 4, 299 (1991). The resist compositionsgenerally comprise a photosensitive acid generator and an acid sensitivepolymer. The polymer has acid sensitive side chain (pendant) groups thatare bonded to the polymer backbone and are reactive towards a proton.Upon imagewise exposure to radiation, the photoacid generator produces aproton. The resist film is heated and, the proton causes catalyticcleavage of the pendant group from the polymer backbone. The proton isnot consumed in the cleavage reaction and catalyzes additional cleavagereactions thereby chemically amplifying the photochemical response ofthe resist. The cleaved polymer is soluble in polar developers such asalcohol and aqueous base while the unexposed polymer is soluble innon-polar organic solvents such as anisole. Thus the resist can producepositive or negative images of the mask depending of the selection ofthe developer solvent. Although chemically amplified resist compositionsgenerally have suitable lithographic sensitivity, in certainapplications, their performance can be improved by (i) increasing theirthermal stability in terms of thermal decomposition and plastic flow and(ii) increasing their stability in the presence of airborne chemicalcontaminants. For example, in some semiconductor manufacturingprocesses, post image development temperatures (e.g. etching,implantation etc.) can reach 200° C. Brunsvold et al., U.S. Pat. Nos.4,939,070 (issued Jul. 3, 1990) and 4,931,379 (issued Jun. 5, 1990)disclose chemically amplified, acid sensitive resist compositions havingincreased thermal stability in the post image development stage.Brunsvold's resist compositions form a hydrogen bonding network aftercleavage of the acid sensitive side chain group to increase the thermalstability of the polymer. Brunsvold avoids hydrogen-bonding moietiesprior to the cleavage reaction because such hydrogen bonding is known tounacceptably destabilize the acid sensitive side chain. AlthoughBrunsvold resists have suitable thermal stability, they also have lowersensitivity and therefore are unsuitable in certain applications.

[0006] With respect to chemical contamination, MacDonald et al. SPIE14662. (1991) reported that due to the catalytic nature of the imagingmechanisms, chemically amplified resist systems are sensitive towardminute amounts of airborne chemical contaminants such as basic organicsubstances. These substances degrade the resulting developed image inthe film and cause a loss of the linewidth control of the developedimage. This problem is exaggerated in a manufacturing process wherethere is an extended and variable period of time between applying thefilm to the substrate and development of the image. In order to protectthe resist from such airborne contaminants, the air surrounding thecoated film is carefully filtered to remove such substances.Alternatively, the resist film is overcoated with a protective polymerlayer. However, these are cumbersome processes.

[0007] Therefore, there was a need in the art for an acid sensitive,chemically amplified photoresist composition having high thermalstability and stability in the presence of airborne chemicalcontaminants for use in semiconductor manufacturing. Apparently, thiswas accomplished in the invention outlined in U.S. Pat. No. 5,625,020which relates to a photosensitive resist composition comprising (i) aphotosensitive acid generator and (ii) a polymer comprisinghydroxystyrene and acrylate, methacrylate or a mixture of acrylate andmethacrylate. The resist has high lithographic sensitivity and highthermal stability. The resist also exhibits surprising stability in thepresence of airborne chemical contaminants. However, one of the problemswith this composition was that the process of preparing the polymer asoutlined in column 3, lines 10-30 and in Example 1 (of U.S. Pat. No.5,625,020) results in poor conversion rates and chemical cleavage ofsome groups in the repeat units. Thus, one of the objects of the presentinvention is an improved process for preparing the polymers used in thephotoresist compositions.

[0008] The processes of the present invention provide methods which arefast, clean, anhydrous, and render the analysis of catalyst used thereinan easy manner. Furthermore, the polymer in solution, if desired can befurther treated to provide a photoresist composition which can bedirectly used without isolating the polymer beforehand.

[0009] 3. Prior Art

[0010] The following references are disclosed as general backgroundinformation.

[0011] 1. U.S. Pat. No. 4,898,916 discloses a process for thepreparation of poly(vinylphenol) from poly(acetoxystyrene) by acidcatalyzed transesterification.

[0012] 2. U.S. Pat. No. 5,239,015 discloses a process for preparing lowoptical density polymers and co-polymers for photoresists and opticalapplications.

[0013] 3. U.S. Pat. No. 5,625,007 discloses a process for making lowoptical polymers and co-polymers for photoresists and opticalapplications.

[0014] 4. U.S. Pat. No. 5,625,020 discloses a process for making aphotoresist composition containing a photosensitive acid generator and apolymer comprising the reaction product of hydroxystyrene with acrylate,methacrylate or a mixture of acrylate and methacrylate.

[0015] 5. EP 0813113 A1, Barclay, discloses an aqueoustransesterification to deprotect the protected polymer.

[0016] 6. WO 94 14858 A discloses polymerizing hydroxystyrene withoutthe protecting group.

[0017] Other patents of interest are U.S. Pat. Nos. 4,679,843;4,822,862; 4,912,173; 4,962,147; 5,087,772; 5,304,610; 5,789,522;5,939,511; and 5,945,251.

[0018] All of the references described herein are incorporated herein byreference in their entirety.

SUMMARY OF THE INVENTION

[0019] This invention relates to a novel “one-pot”, cost efficientprocess for the preparation of hydroxyl containing polymers such ashomo-, co-, and terpolymers of (1) p-hydroxystyrene (PHS) or substitutedp-hydroxystyrene (SPHS) alone or in combination with (2) alkyl acrylates(AA) and/or (3) other monomers such as ethylenically unsaturatedcopolymerizable monomers (EUCM). This unique and novel process involvesmulti-steps depending upon the polymer being formed and which whencompleted yield a hydroxyl containing polymer in solution and havingenhanced purity. The steps start with (1) the polymerization of asubstituted styrene (alive if one is making a homopolymer) orsubstituted styrene and/or AA and/or EUCM in an alcohol solvent in thepresence of a free radical initiator. (2) Purification of the productfrom step (1) by fractionation with an alcohol solvent. (3)Transesterification of the product from step (2) in the presence of acatalyst. (4) Purification of the product from step (3) by anothersolvent, immiscible with the alcohol solvent, under distillationconditions. (5) Catalyst removal via ion exchange of the product fromstep (3). (6) A “Solvent Swap” of the product of step 5 wherein saidalcohol solvent is removed and replaced by a photoresist type solvent.Some preferred embodiments include a substantially pure homopolymers ofp-hydroxystyrene (PHS), copolymers of p-hydroxystyrene, tert-butylacrylate and terpolymer of p-hydroxystyrene, tert-butyl acrylate andstyrene. These hydroxyl containing polymers have a wide variety ofapplications including as photoresists in microelectronics industry.

DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention thus provides, in part, a novel process forproducing polymers that are used in photoresist compositions. Theprocess is an improvement over the prior art and is quite efficient.Specifically, this invention provides a process for the preparation of ahydroxyl containing polymer of I,

[0021] either alone or in combination with an acrylate monomer havingthe formula II,

[0022] and/or with one or more ethylenically unsaturated copolymerizablemonomers (EUCM) selected from the group consisting of styrene,4-methylstyrene, styrene alkoxide wherein the alkyl portion is C₁-C₅straight or branch chain, maleic anhydride, dialkyl maleate, dialkylfumarate and vinyl chloride, wherein alkyl is having 1 to 4 carbonatoms, comprising the following steps.

[0023] Step 1—Polymerization

[0024] In this step, a substituted styrene monomer of formula III,

[0025] wherein R is either —OC(O)R⁵ or —OR⁵; either alone (if preparinga homopolymer) or in combination with said monomer II, and/or one ormore of said copolymerizable monomers (EUCM) is subjected to suitablepolymerization conditions in a carboxylic alcohol solvent and in thepresence of a free radical initiator at suitable temperature for asufficient period of time to produce a polymer of correspondingcomposition.

[0026] In the above formulae I, II, and III, the following are thedefinitions:

[0027] i) R¹ and R² are the same or different and independently selectedfrom the group consisting of:

[0028] hydrogen;

[0029] fluorine, chlorine or bromine;

[0030] alkyl or fluoroalkyl group having the formula C_(n)H_(x)F_(y)where n is an integer from 1 to 4, x and y are integers from 0 to 2n+1,and the sum of x and y is 2n+1; and

[0031] phenyl or tolyl;

[0032] ii) R³ is selected from the group consisting of:

[0033] hydrogen; and

[0034] methyl, ethyl, n-propyl, iso-propyl, n-butyl, i-butyl or t-butyl;

[0035] iii) R⁴ is selected from the group consisting of methyl, ethyl,n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, t-amyl, benzyl,cyclohexyl, 9-anthracenyl, 2-hydroxyethyl, cinnamyl, adamantly, methylor ethyl adamantly, isobornyl, 2-ethoxyethyl, n-heptyl, n-hexyl,2-hydroxypropyl, 2-ethylbutyl, 2-methoxypropyl, 2-(2-methoxyethoxyl),2-naphthyl, 2-phenylethyl, phenyl, and the like.

[0036] iv) R⁵ is C₁-C₅ alkyl, either straight or branch chain.

[0037] It is also within the scope of the present invention to prepare ahomopolymer of formula I from the monomer of formula III. As onepreferred embodiment, polyhydroxystyrene (PHS) can be prepared fromacetoxystyrene monomer (ASM) according to the novel processes set forthherein.

[0038] The scope of the present invention thus covers (a) a homopolymerof formula I derived from formula III monomer; (b) a copolymer derivedfrom formula II and formula III monomers; (c) a copolymer derived fromformula III monomers and the EUCM; and (d) a terpolymer derived frommonomers of formula II, formula III and EUCM.

[0039] In conjunction with formula II (an acrylate monomer) set forthherein, some preferred acrylate monomers are (1) MAA—methyl adamantylacrylate, (2) MAMA—methyl adamantly methacrylate, (3) EAA—ethyladamantyl acrylate, (4) EAMA—ethyl adamantyl methacrylate, (5)ETCDA—ethyl tricyclodecanyl acrylate, (6) ETCDMA—ethyl tricyclodecanylmethacrylate, (7) PAMA—propyl adamantyl methacrylate, (8)MBAMA—methoxybutyl adamantyl methacrylate, (9) MBAA—methoxylbutyladamantyl acrylate, (10) isobomylacrylate, (11) isobornylmethacrylate,(12) cyclohexylacrylate, and (13) cyclohexylmethacrylate.

[0040] Co-polymers having polyhydroxystyrene (PHS) and one or more ofthe above acrylate monomers are some of the materials that are made bythe novel processes of the present invention.

[0041] In another embodiment in this step 1, the reaction mixture mayalso comprise an additional co-solvent. The co-solvent is selected fromthe group consisting of tetrahydrofuran, methyl ethyl ketone, acetone,and 1,4-dioxane.

[0042] The carboxylic alcohol solvent is an alcohol having 1 to 4 carbonatoms and is selected from the group consisting of methanol, ethanol,isopropanol, tert-butanol, and combinations thereof The amount ofsolvent (and/or second solvent) used is not critical and can be anyamount which accomplishes the desired end result.

[0043] The free radical initiator may be any initiator that achieves thedesired end result. The initiator may be selected from the groupconsisting of 2,2′-azobis(2,4-dimethylpentanenitrile),2,2′-azobis(2-methylpropanenitrile), 2,2′-azobis(2-methylbutanenitrile),1,1′-azobis(cyclohexanecarbonitrile), t-butyl peroxy-2-ethylhexanoate,t-butyl peroxypivalate, t-amyl peroxypivalate, diisononanoyl peroxide,decanoyl peroxide, succinic acid peroxide, di(n-propyl)peroxydicarbonate, di(sec-butyl) peroxydicarbonate, di(2-ethylhexyl)peroxydicarbonate, t-butylperoxyneodecanoate,2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane,t-amylperoxyneodecanoate, dimethyl 2,2′-azobisisobutyrate andcombinations thereof.

[0044] As a preferred embodiment, the initiator is selected from thegroup consisting of 2,2′-azobis(2,4-dimethylpentanenitrile),2,2′-azobis(2-metbylpropanenitrile), 2,2′-azobis(2-methylbutanenitrile),1,1′-azobis(cyclohexanecarbonitrile), t-butyl peroxy-2-ethylhexanoate,t-butyl peroxypivalate, t-amyl peroxypivalate, and combinations thereof.

[0045] The amount of initiator is any amount that accomplishes thedesired end result. However, as a preferred embodiment, said initiatoris present to about three mole percent based upon the total moles of allof said monomers I, II, and said copolymerizable monomers.

[0046] The polymerization conditions are any temperature and pressurethat will produce the desired end result. In general, the temperaturesare from about 30° C. to about 100° C., preferably from about 40° C. toabout 100° C., and most preferably from about 45° C. to about 90° C. Thepressure may be atmospheric, sub-atmospheric or super-atmospheric. Thepolymerization time is not critical, but generally will take place overa period of at least one minute in order to produce a polymer ofcorresponding composition.

[0047] Step 2—Purification

[0048] After the polymerization of step 1, and prior to thetransesterification of step 3, the polymer from step 1 is subjected to apurification procedure wherein the same type carboxylic alcoholicsolvent (first solvent) is used to purify the polymer via a multi-stepfractionation process. Additional first solvent is added to the polymermixture of step 1, and the resultant slurry is stirred vigorously and/orheated to boiling (about 66° C.) for several minutes, and then chilledto as low as 25° C. and allowed to stand. This permits the slurry toproduce a phase separation, and then the liquid is removed bycentrifugation, filtration, decantation or by similar means. The processis repeated at least one more time until no further purification isidentified, as for example, until a small sample of the decantedsolvent, upon evaporation to dryness shows substantially no residue.This fractionation process is generally carried out 2 to 10 times, i.e.heating, cooling, separating, and the solvent replacement.

[0049] One of the important measures of the degree of impurity of thecrude polymer produced from the polymerization of the monomers is thepolydispersity value. In general, it is desirable to have a low value,for example, less than about 3; the lower value is indicative that thepolymerization reaction was more uniform in chain length. The uniquenessof this purification step is that the desired polymer formed is, to somedegree, not soluble in the solvent and that the undesired, low molecularweight average polymers and undesired monomers are soluble in thesolvent. Thus the novel purification/fractionalization provides theremoval of these undesirable materials. In general, the polydispersityof the crude polymer is measured before, during and after thispurification/fractionalization step, with the objective of reducing thisvalue by at least about 10% of what the value of the original crudepolymer was before the purification treatment. Preferably, it isdesirable to yield a product whose polydispersity is below about 2.0. Itis to be understood that polydispersity means the ratio of weightaverage molecular weight (Mw) over the number average molecular weight(Mn) as determined by Gel Permeation Chromatography (GPC).

[0050] Step 3—Transesterification

[0051] In transesterification step, the polymer/solvent mixture fromstep 2 is subjected to transesterification conditions in said alcoholsolvent in the presence of a catalytic amount of a transesterificationcatalyst. The catalyst is such that it will not substantially react withthe polymer, or said alkyl acrylate monomer II, or with saidco-polymerizable monomers (EUCM). The catalyst is selected from thegroup consisting of (anhydrous) ammonia, lithium methoxide, lithiumethoxide, lithium isopropoxide, sodium methoxide, sodium ethoxide,sodium isopropoxide, potassium methoxide, potassium ethoxidc, potassiumisopropoxide, cesium methoxide, cesium ethoxide, cesium isopropoxide,and combinations thereof, wherein the carboxylic alkoxide anion issimilar to the carboxylic alcohol solvent. It is also to be understoodthat the catalyst can be alkali metal hydroxides such as lithiumhydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide andcombinations thereof. If the monomer being used is —OR where it is —OR⁵,then the catalyst is a strong acid such as mineral acids such as HCL.

[0052] The amount of catalyst employed is from about 0.1 mole percent toabout 2 mole percent of monomer I present in the composition of saidpolymer.

[0053] In a preferred embodiment, the catalyst is added in step (b) as asolution in said alcohol solvent.

[0054] The temperature in step (b) is such that the transesterifiedby-product ester formed can be continually removed from the reactionmixture to form the polymer of I, II, and said copolymerizable monomer.Such temperatures can be from about 50° C. to about 200° C. In apreferred embodiment, the transesterification reaction is carried out atreflux temperature of said alcohol solvent.

[0055] Step 4—Purification

[0056] This purification step comes before the catalyst removal step(5). According to this step 4, there is added to the polymer in analcoholic solution, a second solvent which is immiscible with saidalcohol solvent until a second layer is formed. The mixture is thenstirred vigorously or is heated to boiling for several minutes and thenallowed to stand until cool. A discrete second layer is formed which isthen removed by decantation or similar means, and the process isrepeated until no further purification is identified, as for example,until a small sample of the decanted second (non-alcohol) solvent uponevaporation to dryness shows no residue. In this fashion, there areremoved by-products and low weight average molecular weight materials.

[0057] The alcoholic solution of the polymer is then subjected todistillation to remove the remaining second solvent, which was misciblein the alcohol. Most often removal of the second solvent is accomplishedby azeotropic distillation; the azeotropic mixture boiling below theboiling temperature of either the alcohol or the second solvent.

[0058] Typical second solvents useful for the method of this stepinclude hexane, heptane, octane, petroleum ether, ligroin, lower alkylhalohydrocarbons, i.e., methylene chloride, and the like.

[0059] Step 5—Catalyst Removal

[0060] In view of the nature of the catalyst employed in step 3, it iscritical that it be removed from the system. In this step, there isemployed a cation-exchange resin preferably a acidic cation exchangeresin, to accomplish the desired end result. An acidic ion exchangeresin, such as sulfonated styrene/divinylbenzene cation exchange resinin hydrogen-form is preferably utilized in the present process. Suitableacidic exchange resins are available from Rohm and Haas Company, e.g.AMBERLYST 15 acidic ion exchange resin. These Amberlyst resins typicallycontain as much as 80,000 to 200,000 ppb of sodium and iron. Beforebeing utilized in the process of the invention, the ion exchange resinmust be treated with water and then a mineral acid solution to reducethe metal ion level. When removing the catalyst from the polymersolution, it is important that the ion exchange resin be rinsed with asolvent that is the same as, or at least compatible with, the polymersolution solvent. The procedure in step (c) may be similar to thoseprocedures disclosed in U.S. Pat. Nos. 5,284,930 and 5,288,850.

[0061] Step 6—Solvent Swap

[0062] In this step, the purified polymer is solvent exchanged with athird or aprotic/organic solvent which is a photoresist compatiblesolvent, and the alcoholic solvent is removed by distillation. Thisthird solvent is at least one member selected from glycol ethers, glycolether acetates and aliphatic esters having no hydroxyl or keto group.Examples of the solvent include glycol ether acetates such as ethyleneglycol monoethyl ether acetate and propylene glycol monomethyl etheracetate (PGMEA) and esters such as ethyl-3-ethoxypropionate,methyl-3-methoxypropionate, among which PGMEA is preferred. Thesesolvents may be used alone or in the form of a mixture thereof.

[0063] Further examples of the third solvent include butyl acetate, amylacetate, cyclohexyl acetate, 3-methoxybutyl acetate, methyl ethylketone, methyl amyl ketone, cyclohexanone, cyclopentanone, 3-ethoxyethylpropionate, 3-ethoxymethyl propionate, 3-methoxymethyl propionate,methyl acetoacetate, ethyl acetoacetate, diacetone alcohol, methylpyruvate, ethyl pyruvate, propylene glycol monomethyl ether, propyleneglycol monoethyl ether, propylene glycol monomethyl ether propionate,propylene glycol monoethyl ether propionate, ethylene glycol monomethylether, ethylene glycol monoethyl ether, diethylene glycol monomethylether, diethylene glycol monoethyl ether, 3-methyl-3-methoxybutanol,N-methylpyrrolidone, dimethylsulfoxide, γ-butyrolactone, propyleneglycol methyl ether acetate, propylene glycol ethyl ether acetate,propylene glycol propyl ether acetate, methyl lactate, ethyl lactate,propyl lactate, and tetramethylene sulfone. Of these, the propyleneglycol alkyl ether acetates and alkyl lactates are especially preferred.The solvents may be used alone or in admixture of two or more. Anexemplary useful solvent mixture is a mixture of a propylene glycolalkyl ether acetate and an alkyl lactate. It is noted that the alkylgroups of the propylene glycol alkyl ether acetates are preferably thoseof 1 to 4 carbon atoms, for example, methyl, ethyl and propyl, withmethyl and ethyl being especially preferred. Since the propylene glycolalkyl ether acetates include 1,2- and 1,3-substituted ones, eachincludes three isomers depending on the combination of substitutedpositions, which may be used alone or in admixture. It is also notedthat the alkyl groups of the alkyl lactates are preferably those of 1 to4 carbon atoms, for example, methyl, ethyl and propyl, with methyl andethyl being especially preferred.

[0064] When the propylene glycol alkyl ether acetate is used as thesolvent, it preferably accounts for at least 50% by weight of the entiresolvent. Also when the alkyl lactate is used as the solvent, itpreferably accounts for at least 50% by weight of the entire solvent.When a mixture of propylene glycol alkyl ether acetate and alkyl lactateis used as the solvent, that mixture preferably accounts for at least50% by weight of the entire solvent. In this solvent mixture, it isfurther preferred that the propylene glycol alkyl ether acetate is 60 to95% by weight and the alkyl lactate is 40 to 5% by weight. A lowerproportion of the propylene glycol alkyl ether acetate would invite aproblem of inefficient coaling whereas a higher proportion thereof wouldprovide insufficient dissolution and allow for particle and foreignmatter formation. A lower proportion of the alkyl lactate would provideinsufficient dissolution and cause the problem of many particles andforeign matter whereas a higher proportion thereof would lead to acomposition which has a too high viscosity to apply and loses storagestability.

[0065] Usually the solvent is used in amounts of about 300 to 2,000parts, preferably about 400 to 1,000 parts by weight per 100 parts byweight of the solids in the chemically amplified positive resistcomposition. The concentration is not limited to this range as long asfilm formation by existing methods is possible.

[0066] Step 7—Addition Reaction Blocking

[0067] The substantially pure hydroxyl containing polymer in solution(i.e. third solvent) from step 6 is then subjected to an additionalreaction to provide said polymer with protective or blocking groups(sometimes referred to as acid labile groups) in order to protect thefunctional/hydroxyl groups. In some cases, this blocking can be eitherfully blocked or partially blocked. In this step, the polymer insolution from step 6 is reacted with a vinyl either compound and/or adialkyl dicarbonate in the presence of a catalyst in the aprotic solvent(i.e. third solvent). When the polymer is reacted with the vinyl ether,it is done in the presence of an acid catalyst followed by adding a basethereto to neutralize it and thus stop the reaction; this is generallycalled an acetalization wherein an acetal derivatized hydroxylcontaining polymer is formed. When the polymer from step 6 is reactedwith a dialkyl dicarbonate, this is an alcoholysis by use of ananhydride (dicarbonate) in the presence of base catalyst which is usedas a reaction catalyst.

[0068] The vinyl ethers suitable for use a protective group includethose falling within the formula

C(R₆)(R₇)═C(R₈)—O—R₉

[0069] Wherein R₆, R₇ and R₈ are independently represent a hydrogen atomor a straight-chain, branched, cyclic or hetero-cyclic alkyl groupcontaining 1 to 6 carbon atoms, and R₉ represents a straight-chain,branched, cyclic or hetero-cyclic alkyl or aralkyl group containing 1 to10 carbon atoms which may be substituted with a halogen atom, an alkoxygroup aralkyl oxycarbonyl group and/or alkyl carbonyl amino group.

[0070] The vinyl ether compounds represented by the general formula,described above include vinyl ethers such as methyl vinyl ether, ethylvinyl ether, n-butyl vinyl ether, tert-butyl vinyl ether, 2-chloro-ethylvinyl ether, 1-methoxyethyl vinyl ether, 1-benzyloxyethyl vinyl etheretc.; and isopropenyl ethers such as isopropenyl methyl ether,isopropenyl ethyl ether etc.

[0071] Preferable examples of cyclic vinyl ethers include3,4-dihydro-2H-pyran etc., and preferable examples of divinyl ethersinclude butanediol-1,4-divinyl ether, ethylene glycol divinyl ether,triethylene glycol divinyl ether etc.

[0072] These vinyl ether compounds can be used alone or in combinationthereof. The vinyl ether compounds in total are used preferably in aratio of 0.1 to 0.7 mol equivalent to the phenolic hydroxyl or carboxylgroup of the alkali-soluble polymer having phenolic hydroxyl or carboxylgroup.

[0073] Preferable examples of the dialkyl dicarbonate used in thepresent invention include di-tert-butyl dicarbonate. As with the vinylether compounds, the amount of the dialkyl dicarbonate used ispreferably 0.1 to 0.7 mol equivalent to the phenolic hydroxyl orcarboxyl group of the alkali-soluble polymer having a phenolic hydroxylor carboxyl group.

[0074] In the present invention, at least one vinyl ether compound andat least one dialkyl dicarbonate can be used simultaneously forprotection of a single alkali-soluble polymer described above.

[0075] If the resist materials to be synthesized are used as a componentof a resist composition exposed with e.g KrF exeimer laser radiation, itis preferable to use a catalyst showing no absorption at 248 nm i.e. theexposure wavelength of KrF exeimer laser. Accordingly, when an acid isused as the reaction catalyst, the acid is not to have a benzene ringpreferably. Examples of acids which can be used as the reaction catalystin the present invention include mineral acids such as hydrochloricacid, sulfuric acid etc., organic sulfonic acids such as methanesulfonicacid, camphorsulfonic acid etc. or halocarboxylic acids such astrifluoroacetic acid, trichloroacetic acid etc. The amount of the acidused is preferably 0.1 to 10 mmol equivalents to the phenolic hydroxylor carboxyl group of the polymer having a phenolic hydroxyl or carboxylgroup.

[0076] In the case where (+/−) camphorsulfonic acid is used as thereaction catalyst in the form of solution thereof in propylene glycolmonomethyl ether acetate, if said solution is heated or stored for along period of time, the propylene glycol monomethyl ether acetate ishydrolyzed to generate propylene glycol monomethyl ether (PGME) by whichthe reaction is significantly inhibited. Accordingly, the solution of(+/−)camphorsulfonic acid in propylene gycol monomethyl ether acetateshould be prepared just before use.

[0077] When a dialkyl dicarbonate is used as a compound to he reactedwith the alkali-soluble polymer having a phenolic hydroxyl or carboxylgroup, a base is used as the reaction catalyst, while when a vinyl ethercompound is used as a compound to be reacted with the alkali-solublepolymer having a phenolic hydroxyl or carboxyl group, a base is used asthe reaction stopper. As these bases, usual bases which are opticallydecomposable or not decomposable and are used as conventional additivesin chemically amplified resists can be preferably used. Examples ofthese bases include ammonia, organic amines such as triethylamine,dicyclohexyl methylamine, etc.; ammonium hydroxides represented bytetramethylammonium hydroxide (TMAH), sulfonium hydroxides representedby triphenylsulfonium hydroxide, iodonium hydroxides represented bydiphenyliodonium hydroxide and conjugated salts of these iodoniumhydroxides, such as triphenylsulfonium acetate, triphenylsulfoniumcamphanate, triphenylsulfonium camphorate etc. These reaction basecatalysts or reaction stoppers are preferably those which when formedinto a resist composition, do not have influence on resist sensitivity,and in particular, optically decomposable bases are preferable. When theamine is present in the resist composition, attention should be paidbecause sensitivity may be lowered. Further, inorganic bases are notpreferable because many of them contain metal ions that contaminate thesubstrate such as silicon wafer etc. If the polymer is neither isolatednor purified according to the method for preparing a resist compositionof the present invention, the main cause for instability of the polymerin the step of isolation and purification thereof can be eliminated. Ifa base is used as the reaction stopper, the stability of the polymer isfurther improved, and even in the case of the polymer having acetate asa protective group, its stability for 2 months or more at roomtemperature is confirmed.

[0078] The conditions for reacting the alkali-soluble polymer having aphenolic hydroxyl or carboxyl group with the vinyl ether compound or thedialkyl dicarbonate may be the same as in the prior art, and thereaction may be conducted under the same conditions as in the prior art.In this reaction, if water is present in the reaction system, the vinylether is decomposed to formaldehyde and alcohol, and the degree ofprotection by the vinyl ether compound becomes lower than the set value.As the drop of the degree of polymer has a significant effect on thethickness loss of the resist film in developer, the moisture contentshould be minimized in the reaction system preferably. That is, if themoisture content in the reaction system is controlled to be as low aspossible, the degree of protection can be in a certain narrow range, tosignificantly reduce variations in degrees of protection as comparedwith the conventional reaction. Accordingly, the moisture content of thereaction solution before the reaction should be measured by Karl Fischermethod in order to confirm that the moisture content is less than about5,000 ppm, preferably less than about 1,000 ppm. For example, if themoisture content is more than 5,000 ppm, attention should be paid suchthat the degree of protection is within a set value, for example byincreasing the amount of the vinyl other compound as necessary. Thereaction temperature and reaction time are e.g. 25° C., and 6 hoursrespectively, but if the protective group is ketal, are e.g. 0° C. and 2hours respectively.

[0079] If a single alkali-soluble polymer is protected by both a vinylether compound and a dialkyl dicarbonate, usually the polymer issubjected to protection reaction with the vinyl ether compound in thepresence of an acid catalyst and then subjected to protection reactionwith the dialkyl dicarbonate in the presence of a base catalyst.

[0080] The usable base includes radiation-sensitive bases or usual basesnot sensitive to radiation. These bases are not necessarily required forresist formulation, but because their addition can prevent thedeterioration of pattern characteristics even in the case where thetreatment step is conducted with delay, so their addition is preferable.Further, their addition also results in improvements in clear contrast.

[0081] Among radiation-sensitive base compounds suitable as bases,particularly preferable examples include e.g. triphenylsulfoniumhydroxide, triphenylsulfonium acetate, triphenylsulfonium phenolate,tris-(4-methylphenyl) sulfonium hydroxide,tris-(4-methylphenyl)sulfonium acetate, tris-(4-methylphenyl)sulfoniumphenolate, diphenyliodonium hydroxide, diphenyliodonium acetate,diphenyliodonium phenolate, bis-(4-tert-butylphenyl)iodonium hydroxide,bis-(4-tert-butylphenyl)iodonium acetate,bis-(4-tert-butylpheny)iodonium phenolate etc.

[0082] Further, the base compounds not sensitive to radiation includee.g. (a) ammonium salts such as tetramethylammonium hydroxide,tetrabutylammonium hydroxide etc., (b) amines such as n-hexylamine,dodecylamine, aniline, dimethylaniline, diphenylamine, triphenylamine,diazabicyclooctane, diazabicycloundecane etc., and (c) basicheterocyclic compounds such as 3-phenylpyridine, 4-phenylpyridine,lutidine and 2,6-di-tert-butylpyridine.

[0083] These base compounds can be used alone or in combination thereof.The amount of the base compound added is determined according to theamount of the photo acid-generating compound and the photoacid-generating ability of the photoacid generator. Usually the basecompound is used in a ratio of 10 to 110 mol %, preferably 25 to 95 mole% relative to the amount of the photo acid-generating compound.

[0084] Step 8—Neutralization

[0085] In this step of the present invention, the step of inactivatingthe acid catalyst by use of the base is an important step. That is,after the reaction of step 7 is finished, the base (for exampletriphenylsulfonium acetate or the like) is added whereby the acidcatalyst is neutralized and inactivated to stop the reaction, so that apolymer solution having storage stability can be obtained.Theoretically, addition of the base in an equivalent amount to the acidis sufficient to inactivate the acid, but because storage stability canbe further secured by adding about 10% excess base, addition of about1.1 equivalents of the base to 1 equivalent of the acid is preferable.This excess base will be taken into consideration in order to determinethe amount of another base added as an additive for preparing theresist.

[0086] It is also feasible in this neutralization step to use an ionexchange material as previously mentioned herein before.

[0087] Step 9—Photoacid Generator Addition

[0088] The resist composition is prepared without isolating the resistmaterial by directly adding to the resist material solution (prepared asdescribed above) a photoacid generating compound capable of generatingan acid upon exposure to actinic radiation (photoacid generator) and ifnecessary a base and additives for improvement of optical and mechanicalcharacteristics, a film forming property, adhesion with the substrate,etc. optionally in the form of a solution. The viscosity of thecomposition is regulated by addition of solvent, if necessary. Thesolvent used in preparing the resist composition is not necessarilylimited to the type of third solvent having been used in step 6, and itis possible to use any other solvent which is conventionally used inpreparation of a resist composition. Further, any photo acid-generatingcompounds and other additives, which are used conventionally inchemically amplified resists, can also be used. The total solid contentin the resist composition is preferably in the range of 9 to 50% byweight, more preferably 15 to 25% by weight, relative to the solvent.

[0089] The photoacid generator is a compound capable of generating anacid upon exposure to high energy radiation. Preferred photoacidgenerators are sulfonium salts, iodonium salts, sulfonyldiazomethanes,and N-sulfonyloxyimides. These photoacid generators are illustratedbelow while they may be used atone or in admixture of two or more.

[0090] Sulfonium salts are salts of sulfonium cations with sulfonates.Exemplary sulfonium cations include triphenylsulfonium,(4-tert-butoxyphenyl)diphenylsulfonium,bis(4-tert-butoxy-phenyl)phenylsulfonium,tris(4-tert-butoxyphenyl)sulfonium,(3-tert-butoxyphenyl)diphenylsulfonium,bis(3-tert-butoxyphenyl)phenylsulfonium,tris(3-tert-butoxyphenyl)sulfonium,(3,4-di-tert-butoxyphenyl)diphenylsulfonium,bis(3,4-di-tert-butoxyphenyl)phenylsulfonium,tris(3,4-di-tert-butoxyphenyl)sulfonium,diphenyl(4-thiophenoxyphenyl)sulfonium,(4-tert-butoxycarbonylmethyloxyphenyl)diphenylsulfonium.tris(4-tert-butoxycarbonylmethyloxyphenyl)sulfonium,(4-tert-butoxyphenyl)bis(4-dimethylaminophenyl)sulfonium,tris(4-dimethylaminophenyl)sulfonium, 2-naphthyldiphenylsulfonium,dimethyl-2-naphthylsulfonium, 4-hydroxyphenyldimethylsulfonium,4-methoxyphenyl-dimethylsulfonium, trimethylsulfonium,2-oxocyclohexylcyclohexyl-methylsulfonium, trinaphthylsulfonium, andtribenzylsulfonium. Exemplary sulfonates includetrifluoromethanesulfonate, nonafluorobutanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluorooethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,4,4-toluenesulfonyloxybenzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, and methanesulfonate. Sulfonium salts based oncombination of the foregoing examples are included. Iodonium salts aresalts of iodonium cations with sulfonates. Exemplary iodinium cationsare arytiodonium cations including diphenyliodinium,bis(4-tert-butylphenyl)iodonium, 4-tert-butoxyphenylphenyliodonium, and4-methoxyphenylphenylodonium. Exemplary sulfonates includetrifluoromethanesulfonate, nonafluorobutanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,4,4-toluenesulfonyloxy-benzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, and methanesulfonate. Iodonium salts based oncombination of the foregoing examples are included.

[0091] Exemplary sulfonyldiazomethane compounds includebissulfonyldiazomethane compounds and sulfonylcarbonyldiazomethanecompounds such as bis(ethylsulfonyl)diazomethane,bis(1-methylpropylsulfonyl)diazomethane,bis(2-methylpropylsulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane,bis(perfluoroisopropylsulfonyl)diazomethane,bis(phenylsulfonyl)diazomethane,bis(4-methylphenylsulfonyl)diazomethane,bis(2,4-dimethylphenylsulfonyl)diazomethane,bis(2-naphthylsulfonyl)diazomethane,4-methylphenylsulfonylbenzoyldiazomethane,tert-butylcarbonyl-4-methylphenylsulfonyldiazomethane2-naphthylsulfonylbenzoyldiazomethane,4-methylphenylsulfonyl-2-naphthoyldiazomethane,methylsulfonylbenzoyldiazomethane, andtert-butoxycarbonyl-4-methylphenylsulfonyldiazotmethane.

[0092] N-sulfonyloxyimide photoacid generators include combinations ofimide skeletons with sulfonates. Exemplary imide skeletons aresuccinimide, naphthalene dicarboxylic acid imide, phthalimide,cyclohexyldicarboxylic acid imide, 5-norbornene-2,3-dicarboxylic acidimide, and 7-oxabicyclo [2,2,1]-5-heptene-2,3-dicarboxylic acid imide.Exemplary sulfonates include trifluoromethanesulfonate,nonafluorobutanesulfonate, heptadecafluorooctanesulfonate,2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate,4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate,toluenesulfonate, benzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, and methanesulfonate,

[0093] Benzoinsulfonate photoacid generators include benzoin tosylate,benzoin mesylate, and benzoin butanesulfonate.

[0094] Pyrogallol trisulfonate photoacid generators include pyrogallol,fluoroglycine, catechol, resorcinol, hydroquinone, in which all thehydroxyl groups are replaced by trifluoromethanesulfonate,nonafluorobutanesulfonate, heptadecafluorooctanesulfonate,2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate,4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate,toluenesulfonate, benzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, and methanesulfonate.

[0095] Nitrobenzyl sulfonate photoacid generators include2,4-dinitrobenzyl sulfonate, 2-nitrobenzyl sulfonate, and2,6-dinitrobenzyl sulfonate, with exemplary sulfonates includingtrifluoromethanesulfonate, nonafluorobutanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, and methanesulfonate. Alsouseful are analogous nitrobenzyl sulfonate compounds in which the nitrogroup on the benzyl side is replaced by a trifluoromethyl group.

[0096] Sulfone photoacid generators include bis(phenylsulfonyl)methane,bis(4-methylphenylsulfonyl)methane, bis(2-naphthylsulfonyl)methane,2,2-bis(phenylsulfonyl)propane, 2,2-bis(4-methylphenylsulfonyl)propane,2,2-bis(2-naphthylsulfonyl)propane,2-methyl-2-(p-toluenesulfonyl)propiophenone,2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane, and2,4-dimethyl-2-(p-toluenesulfonyl)pentan-3-one.

[0097] Photoacid generators in the form of glyoxime derivatives includebis-o-(p-toluenesulfonyl)-α-dimethylglyoxime,bis-o-(p-toluenesulfonyl)-α-diphenylglyoxime,bis-o-(p-toluenesulfonyl)-α-dicyclohexylglyoxime,bis-o-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime,bis-o-(p-toluenesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,bis-o-(n-butanesulfonyl)-α-dimethylglyoxime,bis-o-(n-butanesulfonyl)-α-diphenylglyoxime,bis-o-(n-butanesulfonyl)-α-dicyclohexylglyoxime,bis-o-(n-butanesulfonyl)-2,3-pentanedioneglyoxime,bis-o-(n-butanesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,bis-o-(methanesulfonyl)-α-dimethylglyoxime,bis-o-(trifluoromethanesulfonyl)-α-dimethylglyoxime,bis-o-(1,1,1-trifluoroethanesulfonyl)-α-dimethylglyoxime,bis-o-(tert-butanesulfonyl)-α-dimethylglyoxime,bis-o-(perfluorooctanesulfonyl)-α-dimethylglyoxime,bis-o-(cyclohexylsulfonyl)-α-dimethylglyoxime,bis-o-(benzenesulfonyl)-α-dimethylglyoxime,bis-o-(p-fluorobenzenesulfonyl)-α-dimethylglyoxime,bis-o-(p-tert-butylbenzenesulfonyl)-α-dimethylglyoxime,bis-o-(xylenesulfonyl)-α-dimethylglyoxime, andbis-o-(camphorsulfonyl)-α-dimethylglyoxime.

[0098] Of these photoacid generators, the sulfonium salts,bissulfonyldiazomethane compounds, and N-sulfonyloxyimide compounds arepreferred.

[0099] While the anion of the optimum acid to be generated differsdepending on the ease of scission of acid labile groups introduced inthe polymer, an anion which is nonvolatile and not extremely diffusiveis generally chosen. The preferred anions include benzenesulfonic acidanions, toluenesulfonic acid anions,4,4-toluenesulfonyloxybenzenesulfonic acid anions,pentafluorobenzenesulfonic acid anions, 2,2,2-trifluoroethanesulfonicacid anions, nonafluorobutanesulfonic acid anions,heptadecafluorooctanesulfonic acid anions, and camphorsulfonic acidanions.

[0100] In the chemically amplified positive resist composition, anappropriate amount of the photoacid generator is 0 to 20 parts, andespecially 1 to 10 parts by weight per 100 parts by weight of the solidsin the composition. The photoacid generators may be used alone or in amixture of two or more. The transmittance of the resist film can becontrolled by using a photoacid generator having a low transmittance atthe exposure wavelength and adjusting the amount of the photoacidgenerator added.

[0101] In conjunction with the all steps set forth above, it is criticalthat all steps be conducted on an anhydrous basis, i.e. wherein thewater level is less than about 5,000 parts per million (ppm), in orderto avoid possible side reactions and provide a mechanism to provide aconvenient and direct route to a resist composition without having toisolate the polymer product and then carry out additional processingsteps.

[0102] It is to be understood that in conjunction with the purificationsteps 2 and 4, set forth above, it is within the scope of this inventionto use both of these steps, only one of these steps or neither of thesesteps.

[0103] This invention is further illustrated by the following examplesthat are provided for illustration purposes and in no way limits thescope of the present invention.

EXAMPLES (GENERAL)

[0104] In the Examples that follow, the following abbreviations areused:

[0105] ASM—p-Acetoxystyrene monomer

[0106] t-BPP—tert-butyl peroxypivalate

[0107] THF—Tetrahydrofuran

[0108] GPC—Gel permeation chromatography

[0109] GC—Gas chromatography

[0110] FTIR—Fourier transform infrared spectroscopy

[0111] NMR—Nuclear magnetic resonance spectroscopy, usually of eitherproton, ¹H; and/or carbon 13, ¹³C nuclei.

[0112] DSC—Differential scanning calorimetry

[0113] UV-Vis—Ultraviolet-Visible Spectroscopy

[0114] General Analytical Techniques Used for the Characterization: Avariety of analytical techniques were used to characterize the co- andterpolymers of the present invention that included the following:

[0115] NMR: ¹H and ¹³C NMR spectra were recorded on a Bruker 400 MHzspectrometer with 5 mm probes at 400 and 100 MHz, respectively.

[0116] GPC: GPC was performed on a Waters gel permeation chromatographequipped with refractive index detection.

[0117] GC: GC analysis was performed on a Hewlett Packard Model 5890series II gas chromatograph equipped with a DB-1 column.

[0118] FTIR: FTIR was recorded on a Mattson Genesis Series FTIR.

[0119] DSC: A Perkin Elmer 7700 DSC was used to determine the T_(g)(glass transition temperature) of the co- and terpolymers of thisinvention. The heating rate was maintained at 10° C./minute, generally,over a temperature range of 50° C. to 400° C. The flow rate of nitrogenor air is maintained at 20 mL/min.

[0120] UV-Vis of samples were taken using a Hewlett Packard Vectra486/33VL UV-Vis spectrophotometer.

Example 1 Poly(4-hydroxystyrene) in propyleneglycolmonomethyl EtherAcetate

[0121] To a four neck 12 liter flask, fitted with a mechanical stirrer,condenser, nitrogen inlet and thermowell, 4-acetoxystyrene (2752.3 g,16.97 moles), and methanol (3075.0 g) were added. The flask was purgedwith nitrogen and then heated to reflux (66° C.) over a period of onehour. Then, 2,2′-azobis(2,4-dimethylvaleronitrile) (146.0 g, 0.59 moles)was added to the hot reactor as a slurry in methanol (250 g). Thereactor was heated at reflux for 2 hours and then an additional chargeof 2,2′-azobis(2,4-dimethylvaleronitrile) (24.3 g, 0.1 moles) was done.The reactor was heated for an additional 6 hours and then was cooled toroom temperature.

[0122] The solids were extract by successive replacements of the solventas follows. The reactor was heated to 60° C. with stirring. The heat wasremoved and the reactor was allowed to cool without stirring to 44.3° C.The top layer (899 g) of solvent was removed by suction and was replacedwith methanol (1495 g). The reactor was again heated to 60° C. andcooled to 41.9° C. without stirring. The top layer (1700 g) was againremoved by suction and was replaced with methanol (1705 g). The reactorwas again heated to 60° C. and cooled to 46.2° C. without stirring. Thetop layer (1633 g) was again removed by suction and was replaced withmethanol (1765 g). The reactor was again heated to 60° C. and cooled to45.0° C. without stirring. The top layer (1905 g) was again removed bysuction and was replaced with methanol (1955 g). The reactor was againheated to 60° C. and cooled to 46.0° C. without stirring. The top layer(2145 g) was again removed by suction and was replaced with methanol(2215 g). The reactor was again heated to 60° C. and cooled to 46.0° C.without stirring. The top layer (2241 g) was again removed by suctionand was replaced with methanol (1700 g). All of the solids during eachextraction were analyzed for molecular weight by GPC, table I. Thereactor was then cooled to room temperature.

[0123] The purified poly(4-acetoxystyrene) was converted topoly(4-hydroxystyrene) as follows. The reactor was fitted with a DeanStark trap and condenser. A solution of 25.0 weight percent of Sodiummethoxide in methanol (64.24 g, 0.30 moles) was added to the reactor.The reactor was then heated to reflux (64° C.). The overhead distillatewas removed and replaced with methanol with equal weight. The reactorwas heat at reflux for 7.5 hours. The reactor was then cooled to roomtemperature. This solution was then passed through a column of AmberlystA15 (2″×16″) at 40 mL/min at room temperature to remove the catalyst andthus avoid metal contamination.

[0124] The solvent was exchanged from methanol topropyleneglycolmonomethyl ether acetate (PGMEA) as follows. The solutionwas added to a 4 neck, 12 liter flask fitted with a distillation headand receiver, thermowell, mechanical stirrer, and nitrogen inlet. Thereactor was heated to 25° C. to 48° C. under vacuum (120 torr to 10torr) to remove methanol. To the reactor, a total of 4975 g a PGMEA wasadded as the methanol was removed. The amount of solids present wasdetermined by density and the solution was adjusted to 35.0 weightpercent with PGMEA. An overall yield of 5 1634 g of polymer (81.7%theoretical yield) was obtained.

Example 2 Poly(4-hydroxystyrene) in propyleneglycolmonomethyl EtherAcetate

[0125] To a four neck 12 liter flask, fitted with a mechanical stirrer,condenser, nitrogen inlet and thermowell, 4-acetoxystyrene (2752.3 g,16.97 moles), and methanol (3081.0 g) were added. The flask was purgedwith nitrogen and then heated to reflux (66° C.) over a period of onehour. Then, 2,2′-azobis(2,4-dimethylvaleronitrile) (146.1 g, 0.59 moles)was added to the hot reactor as a slurry in methanol (250 g). Thereactor was heated at reflux for 2 hours and then an additional chargeof 2,2′-azobis(2,4-dimethylvaleronitrile) (24.4 g, 0.01 moles) was done.The reactor was heated for an additional 6 hours and then was cooled toroom temperature.

[0126] The solids were extracted by successive replacements of thesolvent as follows. The reactor was heated to 60° C. with stirring. Theheat was removed and the reactor was allowed to cool without stirring to45.0° C. The top layer (1129 g) of solvent was removed by suction andwas replaced with methanol (1817 g). The reactor was again heated to 60°C. and cooled to 47.0° C. without stirring. The top layer (1627 g) wasagain removed by suction and was replaced with methanol (1624 g). Thereactor was again heated to 60° C. and cooled to 44.0° C. withoutstirring. The top layer (1668 g) was again removed by suction and wasreplaced with methanol (1613 g). The reactor was again heated to 60° C.and cooled to 47.0° C. without stirring. The top layer (1514 g) wasagain removed by suction and was replaced with methanol (1745 g). Thereactor was again heated to 60° C. and cooled to 45.0° C. withoutstirring. The top layer (1822 g) was again removed by suction and wasreplaced with methanol (2288 g). The reactor was again heated to 60° C.and cooled to 43.0° C. without stirring. The top layer (22471 g) wasagain removed by suction and was replaced with methanol (1607 g). All ofthe solids during each extraction were analyzed for molecular weight byGPC, table 1. The reactor was then cooled to room temperature.

[0127] The purified poly(4-acetoxystyrene) was converted topoly(4-hydroxystyrene) as follows. The reactor was fitted with a DeanStark trap and condenser. A solution of 25.0 weight percent of Sodiummethoxide in methanol (64.24 g 0.30 moles) was added to the reactor. Thereactor was then heated to reflux (64° C.). The overhead distillate wasremoved and replaced with methanol with equal weight. The reactor washeat at reflux for 7.5 hours. The reactor was then cooled to roomtemperature. This solution was then passed through a column of AmberlystA15 (2″×16″) at 40 mL/min at room temperature to remove metalcontamination.

[0128] The solvent was exchanged from methanol topropyleneglycolmonomethyl ether acetate (PGMEA) as follows. The solutionwas added to a 4 neck, 12 liter flask fitted with a distillation headand receiver, thermowell, mechanical stirrer, and nitrogen inlet. Thereactor was heated to 25° C. to 48° C. under vacuum (120 torr to 10torr) to remove methanol. To the reactor, a total of 4000 g PGMEA wasadded as the methanol was removed. The amount of solids present wasdetermined by density and the solution was adjusted to 35.0 weightpercent with PGMEA. An overall yield of 1708 g of polymer (85.4%theoretical yield) was obtained. TABLE 1 Molecular weight analysis ofpoly(4-acetoxystyrene) purification by extraction. Example 1 Example 2Weight average Number average Weight average Number average SampleMolecular Weight Molecular Weight Polydispersity Molecular WeightMolecular Weight Polydispersity Original solid 9,556 5,083 1.88 8,8664,501 1.97 1^(st) extraction 9,845 5,594 1.76 9,830 5,093 1.93 2^(nd)extraction 10,009 5,888 1.70 10,049 5,742 1.75 3^(rd) extraction 10,3716,285 1.65 10,112 5,879 1.72 4^(th) extraction 9,921 6,162 1.61 10,3275,969 1.73 5^(th) extraction 10,362 6,476 1.60 9,394 5,559 1.69

Example 3 Poly (hydroxystyrene-co-ethoxyethoxystyrene)

[0129] To a 3L 4 neck round bottom flask containing 1.30 kg, 34.5 wt. %polyhydroxystyrene solution in PGMEA, camphoresulphonic acid, 400 mg wasadded under nitrogen atmosphere and the mixture was stirred at 23° C.for 2 hours for homogeneity. The solution was then cooled to 5° C. and127 g, ethylvinylether was added drop wise with stirring under nitrogenat the reaction temperature between 5° C. to 10° C. (2 hours). After theaddition, the mixture was stirred for additional 6 hours at 5° C.Amberlyst A-21, 33 g which was pretreated with PGMEA was added to thereaction mixture and stirred for 2 hours at 25° C. The resin was removedby filtration and 1.43 kg, 39.3% poly(hydroxystyrene-co-ethoxyethoxystyrene) copolymer solution was obtained.The characterization of the copolymer and the ratio determination weredone by NMR. Hydroxystyrene/ethoxyethoxystyrene ratio was determined tobe 60/40, molecular weight was determined by GPC (polystyrene standard)to be Mw=10,819 with the polydispersity 1.77.

Example 4 Poly (hydroxystyrene-co-t-butoxycarbonyloxystyrene)

[0130] To a 2L round bottom flask containing 1.03 kg, 35.1 wt 1%polyhydroxystyrene solution in PGMEA, p-dimethlyaminopyridine, 0.72 g in11 g PGMEA was added under nitrogen and the mixture was stirred at 23°C. for one hour. Di-t-butyl dicarbonate, 124.4 g was added to thesolution at 23° C. and stirred under nitrogen for 6 hours at 23° C.Vacuum was applied to the solution at 20 mmHg with stirring for 1 hourat 23° C. for removal of carbon dioxide formed as a by-product in thesolution. Dowex Mac-3, 30 g which was pretreated with PGMEA was added tothe reaction mixture and stirred for 2 hours at 23° C. The resin wasremoved by filtration and 1.14 kg, 36.6 wt. % poly(hydroxystyrene-co-t-butoxycarbonyloxystyrene) copolymer solution wasobtained. The characterization of the copolymer and the ratiodetermination were done by NMR.Hydroxystyrene/t-butoxycarbonyloxystyrene ratio was determined to be82/18, molecular weight was determined by GPC to be Mw=11,711 withpolydispersity 1.67.

Example 5

[0131] The following example illustrates the use of step 4—purificationof this invention on the purification of a terpolymer of4-hydroxystyrenelstyrene/tert-butyl acrylate (80/10/10)./8467 g4-acetoxystyrene, 685 g styrene, and 829 g tert-butyl acrylate ispolymerized in 11870 g methanol using 982 g tert-butyl peroxypivalate asa catalyst. A sample of the polymer is isolated for analytical purposes.The remainder is treated with 154 g sodium methoxide and the resultingmethyl acetate is removed by distillation. A second sample is removedfor analysis. Heptanes, 5030 g, is added and a second layer is noted.The mixture is heated at refluxing temperature for 2 hours and allowedto cool. The heptanes are separated and is removed by decantation.Heptanes, 4.7 kg, is added and the mixture is again heated to refluxingtemperatures for 3 hours and allowed to cool. The procedure is repeateda third time with 3.57 kg heptanes. After removal of the heptanes layer,the methanol solution is distilled to remove the remaining heptanes andthe solution is passed over a column of Amberlyst 15 to remove alltraces of metal ions. A small portion of the polymer is isolated byprecipitation with water and dried under reduced pressure with anitrogen purge. The T_(g)=159.4° C. The remaining polymer is treated asset forth in Example 1.

Example 6

[0132] The procedure of Example 5 is repeated except that no heptanesextraction is used prior to precipitation of the resin. In thatinstance, the T_(g)=150.7° C.

Example 7

[0133] The following example illustrates the use of step 4 of thisinvention on the purification of a terpolymer of4-hydroxystyrene/styrene/tert.-butyl acrylate (75/15/10). 1680 g4-acetoxystyrene, 217 g styrene, 175 g, tert-butyl acrylate in 2464 gmethanol and 300 g tetrahydrofuran are polymerized with 280 g VAZO 52(DuPont). A sample of the polymer is isolated for analytical purposes.The remainder is treated with 30.5 g sodium methoxide and the resultingmethyl acetate is removed by distillation. A second sample is removedfor analysis. The T_(g)=146.9° C. Heptanes, 1.2 kg, is added and asecond layer is noted. The mixture is heated at refluxing temperaturefor 2 hours and allowed to cool. A second layer does not form andadditional 1.1 kg heptanes are added. The mixture is heated to refluxingtemperature and then allowed to cool. A total of 1.4 kg of heptanes areremoved by decantation. Heptanes, 1.4 kg are added to the methanolsolution and the mixture is heated to refluxing temperature for 2 hoursand allowed to cool. Heptanes, 1.7 kg, is removed by decantation andreplaced by 1.7 kg fresh heptanes. The mixture is heated to refluxingtemperature for 2 hours and allowed to cool. The heptanes layer isremoved by decantation and the methanol solution is boiled to remove theremaining heptanes. A sample of the polymer is isolated by precipitationwith water and dried under reduced pressure with a nitrogen purge. TheT_(g)=152.3° C. The remaining polymer is treated as set forth in Example1.

Example 8

[0134] The following example illustrates the use of step 4 of thisinvention on the purification of a terpolymer of4-hydroxystyrene/styrene/tert-butyl acrylate (55/25/20) and extractionof the purified terpolymer into ethyl lactate. 1443.4 g4-acetoxystyrene, 424.3 g styrene, 411.0 g, tert-butyl acrylate in 2279g methanol are polymerized with 244.0 g tert-butyl peroxypivalate.Transesterification is accomplished with 26.7 g sodium methoxide in 774g of methanol. The metal ions are removed using Amberlyst 15 resin toprepare a methanolic solution of the polymer. A sample is removed foranalysis. The T_(g)=132.6° C. The solution is extracted three times withheptanes: (1) 3323 g heptanes added and the mixture stirred for 30minutes then allowed to stand 30 minutes. The heptanes layer (2553 g) isremoved and (2) replaced with 3345 g. of fresh heptanes. The mixture isstirred for 30 minutes and allowed to stand for 30 minutes. The heptaneslayer (3755 g) is removed and (3) replaced with 3316 g fresh heptanes.The mixture is stirred for 30 minutes and allowed to stand 30 minutes.The heptanes layer (3678 g.) is removed and the methanol layer isdistilled to remove the remaining heptanes. A second sample is removedfor analysis. The T_(g)=139.5° C. Ethyl lactate, 1119.36 g, is added andthe whole subjected to vacuum distillation at 370-380 torr. When the pottemperature reaches 48.7° C. (overhead temperature of 32° C.), anadditional 743.72 g of ethyl lactate is added, distillation is resumeduntil the pot temperature reaches 73.1° C. (overhead temperature of43%.) An additional 727.29 g of ethyl lactate is added and thedistillation is resumed until the pot temperature reaches 81.2° C.(overhead temperature of 49° C.).

Example 9

[0135] The following example illustrates the use of step 4 of thisinvention on the purification of a copolymer of4-hydroxystyrene/tert-butyl acrylate (75/25). 1048 g 4-acetoxystyrene,272 g, tert-butyl acrylate in 1578 g methanol are polymerized with 63.2g VAZO 52 (DuPont). A sample of the polymer is isolated for analyticalpurposes. The remainder is treated with 19.0 g sodium methoxide and theresulting methyl acetate is removed by distillation. A second sample isremoved for analysis. The T_(g)=138.6° C. Heptanes, 823 g, is added anda second layer is noted. The mixture is stirred at room temperature for1 hr and then allowed to stand for 1 hr. A total of 475 g of heptanes isremoved by decantation and replaced by 838 g of fresh heptanes. Themixture is again stirred at room temperature for 1 hr and then allowedto stand for 1 hr. A total of 929 g of heptanes is removed bydecantation and replaced by 8343 g of fresh heptanes. A total of 1008 gof heptanes is removed by decantation. The methanol solution is boiledto remove the remaining heptanes. A sample of the polymer is isolated byprecipitation with water and dried under reduced pressure with anitrogen purge. The T_(g)=144.7° C. The remaining polymer is treated asset forth in Example 1.

Example 10

[0136] The following example illustrates the use of step 4 of thisinvention on the purification of commercially availablepoly(4-hydroxystyrene). The initial sample had a T_(g)=165.3° C. Asolution of 250 g of poly(4-hydroxystyrene) in 583 g of methanol isextracted three times with heptanes, (1) 343 g heptanes added and themixture stirred for 30 minutes then allowed to stand 30 minutes. Theheptanes layer (289 g) is removed and (2) replaced with 352 g of freshheptanes. The mixture is stirred for 30 minutes and allowed to stand for30 minutes. The heptanes layer (324 g) is removed and (3) replaced with348 g fresh heptanes. The mixture is stirred for 30 minutes and allowedto stand 30 minutes. The heptanes layer (364 g) is removed and themethanol layer is distilled to remove the remaining heptanes. A sampleof the polymer is isolated by precipitation with water and dried underreduced pressure with a nitrogen purge. The T_(g)=172.6° C. Theremaining polymer is treated as set forth in Example 1.

[0137] While specific reaction conditions, reactants, and equipment aredescribed above to enable one skilled in the art to practice theinvention, one skilled in the art will be able to make modifications andadjustments which are obvious extensions of the present inventions. Suchobvious extensions of or equivalents to the present invention areintended to be within the scope of the present inventions, asdemonstrated by the claims which follow.

What is claimed is:
 1. A liquid phase process for preparing an anhydrousand pure hydroxyl containing polymer in solution and which comprises thesteps of: (A) polymerizing a monomer or monomers selected from the groupconsisting of substituted styrene alkyl acrylates, ethylenicallyunsaturated co-polymerizable monomer or monomers and mixtures thereof ina first solvent in the presence of an initiator for a sufficient periodof time and at a sufficient temperature and pressure to form a polymerand first solvent mixture; (B) purifying the polymer and first solventmixture by fractionation wherein additional first solvent is added tosaid mixture, said mixture is heated and/or stirred, the mixture isallowed to settle, the first solvent is decanted, and further firstsolvent is added, and repeating this fractionation at least once more;(C) transesterifying said purified mixture of step (B) wherein saidmixture is refluxed at the boiling point of said first solvent in thepresence of a catalyst for a sufficient period of time and at asufficient temperature and pressure to form a reaction mixturecontaining a hydroxyl containing polymer and first solvent; (D)purifying said reaction mixture from step (C) wherein a second solventis mixed with said reaction mixture in which said second solvent isimmiscible, allowing the layers to separate, and removing said secondsolvent and any dissolved by-products and low weight average molecularweight polymers dissolved therein; (E) passing said purified reactionmixture of step (D) through an ion exchange material in order to removeany catalyst therefrom and thus provide a substantially catalyst-freehydroxyl containing polymer solution; (F) adding a third solvent, whichis photoresist compatible, to said hydroxyl containing polymer solutionfrom step (E) and then distilling off the first solvent at a temperatureof at least the boiling point of said first solvent for a sufficientperiod of time in order to remove substantially all of said firstsolvent to provide a substantially pure hydroxyl containing polymer insolution in said third solvent.
 2. The process as set forth in claim 1wherein when the polydispersity value of the polymer produced in step Ais less than that about 2.0, step B is deleted from the overall process.3. The process as set forth in claim 1 wherein step D is deleted fromthe process.
 4. The process as set forth in claim 1 wherein when thepolymer produced in step A is at least about 40% by weight soluble insaid first solvent, step B is deleted from the overall process.
 5. Theprocess as set forth in claim 1 wherein the second solvent is selectedfrom the group consisting of hexane, heptanes, octane, petroleum ether,ligroin, lower alkyl halohydrocarbons and mixtures thereof.
 6. Theprocess as set forth in claim 5 wherein the second solvent is heptanesand said third solvent is a photoresist compatible solvent.
 7. Theprocess as set forth in claim 1 wherein there is an additional stepafter step (F), wherein the substantially pure hydroxyl containingpolymer in solution is subjected to acetalization wherein said hydroxylcontaining polymer solution is reacted with a vinyl either in thepresence of an acid catalyst for a sufficient period of time and at asufficient temperature and pressure to form an acetal derivatizedhydroxyl containing polymer in solution.
 8. The process as set forth inclaim 7 wherein there is an additional step after the formation of theacetal derivatized hydroxyl containing polymer in solution, wherein saidsolution is neutralized in order to eliminate the acidity thereof. 9.The process as set forth in claim 8 wherein there is an additional stepafter the neutralization step, wherein there is added to saidneutralized acetal derivatized hydroxyl containing polymer in solution,a photoacid generator in order to directly produce a chemicallyamplified resist composition in solution.
 10. The process as set forthin claim 1 wherein the monomer is acetoxystyrene monomer and thepolymerization temperature is from about 30° C. to about 100° C.
 11. Thecomposition of matter produced by the process as set forth in claim 1.12. The composition of matter produced by the process as set forth inclaim
 2. 13. The composition of matter produced by the process as setforth in claim
 7. 14. The composition of matter produced by the processas set forth in claim
 8. 15. The composition of matter produced by theprocess as set forth in claim
 9. 16. The composition of matter producedby the process as set forth in claim 9 wherein said process steps areessentially carried out in one reactor and are carried out entirely inan anhydrous liquid state.
 17. The composition of matter produced by theprocess as set forth in claim 16 wherein said composition of mattercontains less than about 5000 parts per million water.
 18. A liquidphase process for preparing a substantially anhydrous and pure hydroxylcontaining polymer and which comprises the steps of: (A) polymerizingone or more substituted styrenes in a solvent in the presence of aninitiator for a sufficient period of time and at a sufficienttemperature and pressure to form a poly(substituted styrene) and solventmixture; (B) transesterifying said mixture of step (A) wherein saidmixture is refluxed at the boiling point of said solvent in the presenceof a catalyst for a sufficient period of time and at a sufficienttemperature and pressure to form a reaction mixture containing ahydroxyl containing polymer and solvent; (C) passing said reactionmixture of step (B) through an ion exchange material in to remove anycatalyst therefrom and thus provide a substantially catalyst-freehydroxyl containing polymer solution; (D) adding a second solvent tosaid hydroxyl containing polymer solution from step (C) and thendistilling off the first solvent at a temperature of at least theboiling point of said first solvent for s sufficient period of time inorder to remove substantially all of said first solvent to provide asubstantially pure hydroxyl containing polymer in solution in saidsecond solvent.
 19. The process as set forth in claim 18 wherein thereis an additional step after step (D), wherein the substantially purehydroxyl containing polymer in solution is subjected to acetalizationwherein said hydroxyl containing polymer solution is reacted with avinyl ether in the presence of an acid catalyst for a sufficient periodof time and at a sufficient temperature and pressure to form an acetalderivatized hydroxyl containing polymer in solution.
 20. The process asset forth in claim 19 wherein there is an additional step after theformation of the acetal derivatized hydroxyl containing polymer insolution wherein said solution is neutralized in order to eliminate theacidity thereof.
 21. The process as set forth in claim 20 wherein thereis an additional step after the neutralization step, wherein there isadded to said neutralized acetal derivatized hydroxyl containing polymerin solution, a photoacid generator in order to directly produce achemically amplified resist composition in solution.
 22. The process asset forth in claim 18 wherein the substituted styrene is acetoxystyrenemonomer and the polymerization temperature is from about 30° C. to about100° C.
 23. The process as set forth in claim 18 wherein the substitutedstyrene has the formula

wherein R is —OC(O)CH₃; —OC(O)R₁, wherein R₁ is alkyl C₁-C₅; and —OR₁wherein R₁ is the same as above, and either straight chain or branchchain.
 24. The process as set forth in claim 18 wherein there is anadditional step after step (D), wherein the substantially pure hydroxylcontaining polymer in solution is subjected to alcoholysis by use of ananhydride in the presence of an aromatic base to produce a hydroxylcontaining polymer which also contains acid labile groups pendentthereto.
 25. The process as set forth in claim 24 wherein the anhydrideis selected from the group consisting t-butyl esters, t-butylcarbonates, and mixtures thereof.
 26. The process as set forth in claim18 wherein there is also included in said polymerization a vinylmonomer.
 27. The process as set forth in claim 26 wherein the vinylmonomer is acrylic acid esters or methacrylic acid esters.
 28. Theprocess as set forth in claim 18 wherein the hydroxy containing polymeris polyhydroxystyrene.
 29. A liquid phase process for preparing ananhydrous and pure polyhydroxystyrene and which comprises the steps of:(A) polymerizing a substituted acetoxystyrene in a solvent in thepresence of an initiator for a sufficient period of time and at asufficient temperature and pressure to form a polysubstituted acetoxystyrene and solvent mixture; (B) purifying the polysubstitutedacetoxystyrene and solvent mixture by fractionation wherein additionalsolvent is added to said mixture, the mixture is allowed to settle, thesolvent is decanted, and further solvent is added, and repeating thisfractionation at least once more; (C) transesterifying said purifiedmixture of step (B) wherein said mixture is refluxed at the boilingpoint of said solvent in the presence of a catalyst for a sufficientperiod of time and at a sufficient temperature and pressure to form areaction mixture containing polyhydroxystyrene and solvent; (D) passingsaid reaction mixture of step (C) through an ion exchange material in toremove any catalyst therefrom and thus provide a substantiallycatalyst-free polyhydroxystyrene solution; (E) adding a second solventto said polyhydroxystyrene solution from step (D) and then distillingoff the first solvent at a temperature of at least the boiling point ofsaid first solvent for a sufficient period of time in order to removesubstantially all of said first solvent to provide a substantially purepolyhydroxystyrene in solution in said second solvent.
 30. The processas set forth in claim 29 wherein there is an additional step after step(E), wherein the substantially pure polyhydroxystyrene in solution issubjected to acetalization wherein said polyhydroxystyrene solution isreacted with a vinyl either in the presence of an acid catalyst for asufficient period of time and at a sufficient temperature and pressureto form an acetal derivatized polyhydroxystyrene in solution.
 31. Theprocess as set forth in claim 30 wherein there is an additional stepafter the formation of the acetal derivatized polyhydroxystyrene insolution, wherein said solution is neutralized in order to eliminate theacidity thereof.
 32. The process as set forth in claim 31 wherein thereis an additional step after the neutralization step, wherein there isadded to said neutralized acetal derivatized polyhydroxystyrene insolution, a photoacid generator in order to directly produce achemically amplified resist composition in solution.
 33. The process asforth in claim 29 wherein the substituted acetoxystyrene isacetoxystyrene monomer and the polymerization temperature is from about30° C. to about 100° C.
 34. The process as set forth in claim 29 whereinthere is an additional step after step (E), wherein the substantiallypure polyhydroxystyrene in solution is subjected to alcoholysis by useof an anhydride in the presence of an aromatic base to produce apolyhydroxystyrene which also contains acid labile groups pendentthereto.
 35. The process as set forth in claim 34 wherein the anhydrideis selected from the group consisting t-butyl esters, t-butylcarbonates, and mixtures thereof.
 36. The process as set forth in claim29 wherein there is also included in said polymerization a vinylmonomer.
 37. The process as set forth in claim 36 wherein the vinylmonomer is acrylic acid esters or methacrylic acid esters.
 38. Thecomposition of matter produced by the process as set forth in claim 32wherein said process steps are essentially carried out in one reactorand are carried out entirely in a liquid state.
 39. The composition ofmatter produced by the process as set forth in claim 38 wherein saidcomposition of matter contains less than about 5000 parts per millionwater.
 40. The process as set forth in claim 1 wherein step B isdeleted.
 41. The process as set forth in claim 1 wherein step D isdeleted.
 42. The process as set forth in claim 1 wherein both steps Band D are deleted.